Lighting systems wherein light transmitting plates are used are known in the art. US2010020531, for instance, describes a back lighting unit in which lower and upper surfaces of a light transmitting plate function as incident and exit surfaces of light, respectively, and a luminescent material film structure for wavelength-converting the light is provided at a position which the light is incident on or exits from said plate. The in US2010020531 described back lighting unit includes a light emitting means including a light emitting diode disposed to emit light upwards, a light transmitting plate disposed over the light emitting diode, having a lower surface allowing light to be incident thereon and an upper surface allowing light to exit therefrom, and a luminescent material film structure including a particulate luminescent material, formed on at least one of the lower and upper surfaces of the light transmitting plate.